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Date: | Thu, 19 Jan 2006 13:43:24 -0500 |
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Possible low copper foil peel strengths. PTFE and Ceramic HydroCarbons
have fairly low peel strengths, but are less affected by temperature
excursion like FR4 and other thermo-setting resins. Your PCB supplier
should have copper foil peel strength numbers from monthly testing and a
drop off would be noticeable. Construction also has an impact on bond
strength as well as copper foil type.
Jeffrey Bush
Director, Quality Assurance and Technical Support
VERMONT CIRCUITS INCORPORATED
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302
Voice - 802.257.4571 ext 37
Fax - 802.257.0011
<http://www.vtcircuits.com/>
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, January 19, 2006 11:43 AM
To: [log in to unmask]
Subject: [TN] PWB SMT pad retention
Hi, Folks,
Is there a standard that specifies how well SMT pads should adhere to
the pwb? By pads I mean BGA pads that have no trace attachment, and I.C.
(gullwing) pads.
A client has circuit boards with pads that come off extremely easily
during standard rework and reflow processes. It is not limited to the
BGA pads, many other unused I.C. lead pads are also being found out of
place in the solder joints after reflow, and are easily peeled away. The
pads are not tiny flip chip pads, but standard .035" diameter pads and
rectangular .020" by .030" pads. The reflow peak temperature is only 210
deg. C for about 40 seconds. The rework is at 200 C. for 30 seconds.
Also, any speculation on the cause? This problem is limited to a single
PWB part number.
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